Transactional email vs marketing email

The difference in one line

If a person did something and this email is the direct result (signed up, bought, asked to reset a password), it is transactional. If you decided to send it to a group because you have something to say, it is marketing.

Examples

• Transactional: password resets, sign-in links, order confirmations and receipts, shipping updates, invoices, security alerts, a reply to a support request.
• Marketing: newsletters, product announcements, promotions, sales, event invitations, re-engagement campaigns.

How the rules differ

• Consent. Marketing email needs people to have agreed to receive it, with the exact rules depending on where your recipients live (CAN-SPAM in the US, CASL in Canada, GDPR in the EU and UK). Transactional email generally does not need that consent, but it must stay about the transaction.
• Unsubscribe. Marketing email must have an easy unsubscribe. Transactional email does not, and a password reset should not have one.
• Content. Adding promotions to a receipt can turn it into a marketing message under some laws. Keep transactional mail to the transaction.
• Mailbox rules. Gmail and Yahoo require one-click unsubscribe for marketing and subscribed mail. See their requirements.

Why to keep them apart

Marketing mail gets more complaints and more unsubscribes than receipts and resets. If both go out from one domain and a campaign draws complaints, your password-reset emails can start landing in spam. Send them from different subdomains (for example mail.example.com and news.example.com) so each builds its own reputation.

This is general information, not legal advice. Check the rules for the countries you send to.

How to send each

• Transactional: call an email API from your app when the event happens, with an idempotency key so a retry never sends twice.
• Marketing: keep an audience of people who opted in, use a signup form with confirmation, send broadcasts with an unsubscribe link, and watch your complaint rate.